Adaptive antenna control method and adaptive antenna transmission/reception characteristic control method

ABSTRACT

An adaptive antenna control method is used for a radio communication system built by a plurality of radio base stations and a plurality of terminal stations capable of communicating with the radio base stations. Each radio base station includes an adaptive antenna having a plurality of antenna elements, a distributor for generating signals to be input to the plurality of antenna elements by branching a signal of one system to be transmitted, and weighting circuits for respectively weighting transmission signals to the plurality of antenna elements. For reception by each terminal station, an interference wave power given by the transmission signal from each of the plurality of radio base stations is estimated. A weight in the adaptive antenna of each radio base station is determined to minimize a sum of square errors between reception signals and desired signals for all the radio base stations which simultaneously use the same communication channel. An adaptive antenna transmission/reception characteristic control method is also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates to an adaptive antenna control method andadaptive antenna transmission/reception characteristic control method,which can be used to, e.g., improve the frequency use efficiency in aradio communication system having a plurality of base stations bysuppressing interference from a neighboring base station.

In a radio communication system that forms a planar service area, suchas a mobile communication system, radio zones formed by a number of basestations are combined to construct a wide service area. Radio zonesformed at separate positions simultaneously use the same frequency asradio signals. With this method, the frequency use efficiency can beimproved.

Forming hexagonal zones is most effective to minimize, in each radiozone, interference from the remaining radio zones.

For example, as indicated by reference (Okumura and Shinji,“Fundamentals of Mobile Communications”, p. 195), when a service area isconstructed by hexagonal zones, the number K of frequencies required bythis radio communication system is given by

K=(1/3)×(D/R)²

D: the distance between base stations of cells (radio zones) which usethe same frequency

R: the radius of a cell

When each cell has a regular hexagonal shape, (D/R>3) must hold. Hence,the number K of frequencies is at least three.

For the above reason, to provide a communication service in a wideservice area using a conventional typical radio communication system, atleast three radio frequencies must be used.

When an adaptive antenna is employed, interference from another radiozone that uses the same frequency can be suppressed.

For example, a typical adaptive antenna as shown in reference (R. A.Monzingo and T. W. Miller, “Introduction to Adaptive Arrays”, John Wiley& Sons, Inc. 1980) has an arrangement shown in FIG. 9.

Referring to FIG. 9, this adaptive antenna comprises N antenna elements901(1) to 901(N), weighting circuits 902(1) to 902(N) and 912(1) to912(N), weight control unit 903, reference signal generation unit 904,divider/combiner 905, and distributor 913.

The weighting circuits 902(1) to 902(N) and divider/combiner 905 areused for reception. The weighting circuits 912(1) to 912(N) anddistributor 913 are used for transmission. Each weighting circuit 902weights the signal from a corresponding antenna element 901 with acomplex number. The weight control unit 903 controls the value of theweight to be supplied to each weighting circuit 902 or 912. Thedivider/combiner 905 generates a signal by combining the signals of Nsystems, which are weighted by the respective weighting circuits 902.The distributor 913 distributes a signal to be transmitted to systemsequal in number to the antenna elements 901.

When signals received by the antenna elements 901(1) to 901(N) arerepresented by x(1) to x(N), the values of weights in the weightingcircuits 902(1) to 902(N) are represented by w(1) to w(N), and a desiredsignal component is represented by d, a weight WOPT for minimizing theerror between the desired signal component d and the reception signalobtained at the output of the divider/combiner 905 is given by

$\begin{matrix}{W_{opt} = {R_{xx}^{- 1}r_{xd}}} & (13) \\{R_{xx} = {E\left\lfloor {X^{*}X^{T}} \right\rfloor}} & (14) \\{r_{xd} = \begin{pmatrix}\overset{\_}{{x(1)} \cdot d^{*}} \\\overset{\_}{{x(2)} \cdot d^{*}} \\\vdots \\\overset{\_}{{x(N)} \cdot d^{*}}\end{pmatrix}} & (15) \\{{X = \begin{pmatrix}{x(1)} \\{x(2)} \\\vdots \\{x(N)}\end{pmatrix}}{W_{opt} = \begin{pmatrix}{w_{opt}(1)} \\{w_{opt}(2)} \\\vdots \\{w_{opt}(N)}\end{pmatrix}}} & (16)\end{matrix}$

where

suffix *: conjugate transposition

suffix T: transposition

E[·]: expected value

X: input signal vector

x(i): reception signal of ith antenna element

d: desired signal

w_(opt)(i): weight for ith antenna element

When the directional pattern of the antenna is controlled by generatingsuch a weight, a null is formed in the directional pattern with respectto the direction of an interference station. Hence, the influence of theinterference wave from the interference station can be suppressed. A“null” means that the radiation field or reception field strengthbecomes 0.

By installing an adaptive antenna in a base station, even when, e.g.,communication is executed using the same radio frequency in adjacentradio zones, the influence of an interference wave from a neighboringradio zone can be suppressed.

However, assume that a base station uses an adaptive antenna, andanother base station (interference station) that uses the same frequencyas that of the n station (base station) is present in the direction of atarget terminal station viewed from the base station. In this case, ifthe directional pattern of the antenna is controlled to suppress theinfluence of the interference wave from the interference station, thesignal from the target terminal station is also suppressed, and thetransmission quality inevitably degrades.

In a radio communication system, limited frequency resources must beeffectively used. However, in a radio communication system whichprovides a radio communication service in a wide range using a pluralityof base stations, as described above, since interference from aneighboring zone to a given base station and interference from the givenbase station to the neighboring zone are present, zones adjacent to eachother cannot use the same frequency.

When an adaptive antenna is used, the interference wave from aneighboring zone can be suppressed, and therefore, the same radiofrequency can be used in adjacent radio zones. However, no sufficientinterference reduction capability can be obtained only with the controlof a conventional adaptive antenna. Especially, when a target terminalstation is present in the direction of the zone of the neighboring basestation, the interference unavoidably increases.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an adaptive antennacontrol method and adaptive antenna transmission/receptioncharacteristic control method capable of improving the frequency useefficiency in a radio communication system.

In order to achieve the above object, according to the presentinvention, there is provided an adaptive antenna control method used fora radio communication system built by a plurality of radio base stationsand a plurality of terminal stations capable of communicating with theradio base stations, each radio base station including an adaptiveantenna having a plurality of antenna elements, a distributor forgenerating signals to be input to the plurality of antenna elements bybranching a signal of one system to be transmitted, and weightingcircuits for respectively weighting transmission signals to theplurality of antenna elements, wherein for reception by each terminalstation, an interference wave power given by the transmission signalfrom each of the plurality of radio base stations is estimated, and aweight in the adaptive antenna of each radio base station is determinedto minimize a sum of square errors between reception signals and desiredsignals for all the radio base stations which simultaneously use thesame communication channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sequence chart showing the control sequence of an adaptiveantenna control method related to a downlink according to the firstembodiment;

FIG. 2 is a sequence chart showing the control sequence of the adaptiveantenna control method related to an uplink according to the firstembodiment;

FIG. 3 is a block diagram showing the arrangement of a communicationsystem;

FIG. 4 is a flow chart showing control of an intensive control stationrelated to a downlink according to the second embodiment;

FIG. 5 is a flow chart showing control of the intensive control stationrelated to an uplink according to the second embodiment;

FIG. 6 is a graph showing the characteristic of the downlink of thefirst embodiment;

FIG. 7 is a graph showing the characteristic of the uplink of the firstembodiment;

FIG. 8 is a graph showing the characteristic of the second embodiment;

FIG. 9 is a block diagram showing the arrangement of an adaptiveantenna; and

FIG. 10 is a view for explaining the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described below with reference to theaccompanying drawings.

First Embodiment

An adaptive antenna control method according to an embodiment of thepresent invention will be described with reference to FIGS. 1 to 3, 6,and 7. This first embodiment corresponds to claims 1 to 4 and 6 to 9.

FIG. 1 shows the control sequence of the adaptive antenna control methodrelated to a downlink according to the first embodiment. FIG. 2 showsthe control sequence of the adaptive antenna control method related toan uplink according to the first embodiment. FIG. 3 shows thearrangement of a communication system. FIG. 6 shows the characteristicof the downlink of the first embodiment. FIG. 7 shows the characteristicof the uplink of the first embodiment.

In the first embodiment, assume that the present invention is applied tocontrol a communication system as shown in FIG. 3. That is, a pluralityof terminal stations 101 are present in a relatively narrow area. Eachterminal station 101 can execute radio communication with a plurality ofbase stations 102. That is, each terminal station 101 can communicatewith another terminal through any one of the base stations 102.

In this example, assume that the plurality of terminal stations 101 andthe plurality of base stations 102 simultaneously use the samecommunication channel, and space division multiple transmission isimplemented using, e.g., the directivity of an antenna. For thesepurposes, each base station 102 has an adaptive antenna which basicallyhas the same arrangement as that shown in FIG. 9. Additionally, in thisexample, assume that each terminal station 101 has a transmission poweradjustment function.

The plurality of base stations 102 are connected to an intensive controlstation 103 through a wired network. The base stations 102 and intensivecontrol station 103 may be connected through a wireless network. Theintensive control station 103 concentrically controls the plurality ofbase stations 102 and the plurality of terminal stations 101 andcontrols the directional pattern of the antenna in each base station 102and the transmission power of each terminal station 101.

In the example shown in FIG. 3, three terminal stations 101 and threebase stations 102 are controlled. However, the number of terminalstations 101 and the number of base stations 102 are changed as needed.For the adaptive antennaes, the plurality of base stations 102 need notalways have antenna elements in equal number. Control of a downlinkrelated to communication from the base station 102 to the terminalstation 101 and control of an uplink related to communication from theterminal station 101 to the base station 102 are independently executed.

Downlink control will be described first with reference to FIG. 1. Forthe descriptive convenience, this example assumes that the base station102(2) and terminal station 101(1) communicate, and control is executedto suppress the interference for reception at the terminal station101(1) by signals transmitted from the remaining two base stations102(1) and 102(3) which use the same communication channel.

Referring to FIG. 1, first, each of the base stations 102(1), 102(2),and 102(3) transmits a predetermined known signal St to the terminalstation 101(1). In this case, the signals St are transmitted usingdifferent communication channels. That is, communication channels forwhich at least one of the frequency, timing, and spreading code isdifferent are used.

In step S11, the terminal station 101(1) checks the correlation betweenthe signal (St) held by itself and each of the reception signalsreceived from the base stations 102 via the different communicationchannels, thereby estimating a transfer function. A transfer function isobtained for each antenna element of each base station 102.

To estimate a transfer function, a method indicated by, e.g., reference(D. Gerlach and A. Paulraj, Acoustics, Speech and Signal Processing,ICASSP, vol. 4, pp. IV/97-IV100, 1994) is used.

All transfer functions estimated by the terminal station 101(1) aretransferred to the intensive control station 103 through the basestation 102(2) in this case. On the basis of the transfer functionreceived for each base station, the intensive control station 103determines a weight vector for the adaptive antenna in each of the basestations 102(1), 102(2), and 102(3) such that the interference power atthe terminal station 101(1) is minimized.

Assume that the nth base station 102 communicates with the mth terminalstation 101. An interference power U(m) received by the mth terminalstation 101 is given by

$\begin{matrix}{{U(m)} = {\sum\limits_{\underset{({k \neq n})}{k = 1}}^{N}{{\sum\limits_{j = 1}^{P}{{{wd}\left( {k,j} \right)}{{Vd}\left( {m,k,j} \right)}}}}^{2}}} & (21)\end{matrix}$

-   -   wd(k,j): weight for antenna element in downlink    -   Vd(m,k,j): transfer function of antenna element in downlink    -   P: number of antenna elements    -   N: number of base stations

When the plurality of terminal stations 101 are simultaneouslycommunicating, the interference is preferably reduced for the entiresystem. For example, in a communication channel with a lowesttransmission quality, the transmission power of the base station 102 ispreferably increased. In a communication channel with a hightransmission quality, no problem is posed even when the transmissionpower of the base station 102 is suppressed.

To control the interference on the plurality of terminal stations 101altogether, the intensive control station 103 executes control byobtaining an evaluation index Edown of the entire downlink from

$\begin{matrix}{{Edown} = {\sum\limits_{k = 1}^{K}{U(k)}}} & (22)\end{matrix}$

K: number of terminal stations

That is, the intensive control station 103 selects a combination ofweight vectors for the base stations 102, with which the evaluationindex Edown is minimized, thereby suppressing degradation intransmission quality due to the interference to the minimum.

As shown in FIG. 1, the weight vectors determined by the intensivecontrol station 103 are transferred to the base stations 102(1), 102(2),and 102(3). Each of the base stations 102(1), 102(2), and 103(3)supplies to a weighting circuit 912 of the adaptive antenna the weightvector assigned to itself by the intensive control station 103. Withthis processing, the directional patterns of the antennas of the basestations 102(1), 102(2), and 102(3) are determined.

The characteristic of the downlink in executing the control shown inFIG. 1 was simulated using a computer. FIG. 6 shows the result comparedwith a conventional method. This simulation was done assuming thefollowing conditions. All base stations and terminal stations werecompletely synchronized, and the base stations and terminal stationstransmitted signals with the same frequency, timing, and spreading code.

-   -   Radius of cell formed by base station: 250 m    -   Number of antenna elements of adaptive antenna of each base        station: 4 elements    -   Layout of antenna elements: circular array    -   Directivity of antenna element:    -   omni-directional in horizontal plane    -   Antenna element spacing: 0.5 λ    -   Delay profile: exponential model    -   Delay spread: 0.1 symbol length    -   Number of base stations: 36    -   Number of terminal stations: 36    -   Angular spread of incoming wave: 120°

For the conventional method, assume that the adaptive antennaes wereindividually controlled for the respective base stations, as shown in,e.g., reference (R. A. Monzingo and T. W. Miller, “Introduction toAdaptive Arrays”, John Wiley & Sons, Inc. 1980).

The layout of the terminal stations was changed 100 times at random, andthe 50% value of the cumulative probability of the transmission qualityof a terminal station with a lowest transmission quality was evaluated.In addition, assume that one terminal station executed transfer functionestimation with respect to each of three base stations. The number oftimes of weight update by the algorithm of the present invention was100.

Referring to FIG. 6, the distances between base stations are comparedabout the characteristics at 10 dB of the ordinate. The distance betweenbase stations is 600 m for the conventional autonomous distributedcontrol. However, it can be shortened to 400 m, i.e., about ⅔ or less,in the present invention.

That is, when the adaptive antennaes of a plurality of base stations arecontrolled altogether, the transmission quality of a communicationchannel whose transmission quality considerably degrades can beimproved, and the interference in the downlink can be reduced in theentire system

Uplink control will be described next with reference to FIG. 2. For thedescriptive convenience, this example assumes that the base station102(1) and terminal station 101(1) communicate, and control is executedto suppress the interference for reception at the base station 102(1) bysignals transmitted from the remaining two terminal stations 101(2) and101(3) which use the same communication channel and also to reduceinterference for all the plurality of base stations 102(1), 102(2), and102(3).

Although the terminal stations 101(2) and 101(3) are not illustrated inFIG. 2, they perform the same operation of that of the terminal station101(1). Referring to FIG. 2, first, the terminal station 101(1)transmits the predetermined known signal St to each of the base stations102(1), 102(2), and 102(3). In this case, the signals St are transmittedusing different communication channels. That is, communication channelsfor which at least one of the frequency, timing, and spreading code isdifferent are used.

In step S31, each of the base stations 102(1), 102(2), and 102(3) checksthe correlation between the signal (St) held by itself and the receptionsignal received from the terminal station 101(1), thereby estimating atransfer function. A transfer function is obtained for each antennaelement of each base station 102. In addition, the base stations 102(1),102(2), and 102(3) individually estimate transfer functions for each ofthe plurality of terminal stations 101(1), 101(2), and 101(3).

To estimate a transfer function, a method indicated by, e.g., reference(D. Gerlach and A. Paulraj, Acoustics, Speech and Signal Processing,ICASSP, vol. 4, pp. IV/97- IV100, 1994) is used. All transfer functionsestimated by the base stations 102(1), 102(2), and 102(3) aretransferred to the intensive control station 103.

On the basis of the transfer function received for each antenna element,each base station, or each terminal station, the intensive controlstation 103 determines a weight vector for the adaptive antenna in eachof the base stations 102(1), 102(2), and 102(3) and the transmissionpower of each of the terminal stations 101(1), 101(2), and 101(3) suchthat the interference power at all the base stations 102(1), 102(2), and102(3) is minimized.

Assume that the nth base station 102 communicates with the mth terminalstation 101. An interference power U(n) that the nth base station 102receives from the plurality of terminal stations 101 other than the mthterminal station 101 is given by

$\begin{matrix}{{U(n)} = {\sum\limits_{k = {1{({k \neq m})}}}^{K}{{\sum\limits_{j = 1}^{P}{{{wu}\left( {k,j} \right)}{{Vu}\left( {m,k,j} \right)}}}}^{2}}} & (23)\end{matrix}$

-   -   wu(k,j): weight for antenna element in uplink    -   Vu(m,k,j): transfer function of antenna element in uplink    -   P: number of antenna elements    -   N: number of base stations

When the plurality of base stations 102 are simultaneouslycommunicating, the interference is preferably reduced for the entiresystem. For example, when the interference power at the base station102(1) is small but that at the base station 102(2) is large, thetransmission quality in the entire communication system degrades, andthis need be improved. Hence, in a communication channel with a lowesttransmission quality, the transmission power of the terminal station 101is preferably increased. In a communication channel with a hightransmission quality, no problem is posed even when the transmissionpower of the terminal station 101 is suppressed.

To control the interference on the plurality of base stations 102altogether, the intensive control station 103 executes control byobtaining an evaluation index Eup of the entire uplink from

$\begin{matrix}{{Eup} = {\sum\limits_{k = 1}^{N}{U(k)}}} & (24)\end{matrix}$

-   -   N: number of base stations

That is, the intensive control station 103 selects a combination ofweight vectors for the base stations 102 and a combination oftransmission powers of the terminal stations 101, with which theevaluation index Eup is minimized, thereby suppressing degradation intransmission quality due to the interference to the minimum.

As shown in FIG. 2, the weight vectors determined by the intensivecontrol station 103 are transferred to the base stations 102(1), 102(2),and 102(3). In addition, the values of transmission powers determined bythe intensive control station 103 are transferred to the terminalstations 101 through the base stations 102.

Each of the base stations 102(1), 102(2), and 103(3) supplies to theweighting circuit 912 of the adaptive antenna the weight vector assignedto itself by the intensive control station 103. With this processing,the directional patterns of the antennas of the base stations 102(1),102(2), and 102(3) are determined. Each terminal station 101 adjusts itstransmission power in accordance with the transmission power assigned bythe control of the intensive control station 103.

The characteristic of the uplink in executing the control shown in FIG.2 was simulated using a computer. FIG. 7 shows the result compared witha conventional method. This simulation was done assuming the followingconditions.

All base stations and terminal stations were completely synchronized,and the base stations and terminal stations transmitted signals with thesame frequency, timing, and spreading code.

-   -   Radius of cell formed by base station: 250 m    -   Number of antenna elements of adaptive antenna of each base        station: 4 elements    -   Layout of antenna elements: circular array    -   Directivity of antenna element:    -   omni-directional in horizontal plane    -   Antenna element spacing: 0.5 λ    -   Delay profile: exponential model    -   Delay spread: 0.1 symbol length    -   Number of base stations: 36    -   Number of terminal stations: 36    -   Angular spread of incoming wave: 1200

For the conventional method, assume that the adaptive antennaes wereindividually controlled for the respective base stations, and eachterminal station controlled its transmission power such that thereception level at the base station had a predetermined value.

The layout of the terminal stations was changed 100 times at random, andthe 50% value of the cumulative probability of the transmission qualityof a terminal station with a lowest transmission quality was evaluated.In addition, assume that one terminal station executed transfer functionestimation with respect to each of three base stations. The number oftimes of weight update by the algorithm of the present invention was100.

Referring to FIG. 7, the distances between base stations are comparedabout the characteristics at 10 dB of the ordinate. The distance betweenbase stations is 600 m for the conventional autonomous distributedcontrol. However, it can be shortened to 400 m, i.e., about ⅔ or less,in the present invention.

That is, when the adaptive antennaes of a plurality of base stations arecontrolled altogether, the transmission quality of a communicationchannel whose transmission quality considerably degrades can beimproved, as in the downlink, and the interference in the uplink can bereduced in the entire system

Second Embodiment

An adaptive antenna control method according to another embodiment ofthe present invention will be described with reference to FIGS. 4, 5,and 8. This second embodiment corresponds to claims 5 and 10.

FIG. 4 shows control of an intensive control station related to adownlink according to the second embodiment

FIG. 5 shows control of the intensive control station related to anuplink according to the second embodiment.

FIG. 8 shows the characteristic of the second embodiment. The secondembodiment is a modification to the first embodiment. The secondembodiment is the same as the first embodiment except that the contentsof control by an intensive control station 103 are changed as shown inFIGS. 4 and 5. For the same parts as in the first embodiment, adescription thereof will be omitted.

Control of the downlink will be described first with reference to FIG.4. As in FIG. 1, transfer functions estimated by a terminal station101(1) are input to the intensive control station 103 through basestations 102. On the basis of the transfer functions, the intensivecontrol station 103 determines the downlink directional pattern of theantenna of each base station 102. When transfer functions necessary forcontrol are input, processing by the intensive control station 103advances from step S21 to S22. In step S22, a conventional adaptiveantenna control algorithm (e.g., R. A. Monzingo and T. W. Miller,“Introduction to Adaptive Arrays”, John Wiley & Sons, Inc. 1980) isapplied to each base station 102, thereby obtaining the downlink weightvector of the adaptive antenna of each base station 102 for autonomousdistributed control.

$\begin{matrix}{{{Wd}(n)} = {{G(m)}\left( {\sum\limits_{k = 1}^{K}{{G(k)}^{2}{{Vd}\left( {k,n} \right)}{{Vd}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vd}\left( {m,n} \right)}}} & (25) \\{{G(m)} = \frac{{Re}\left( {{{Wd}(n)}^{H}{{Vd}\left( {m,n} \right)}} \right)}{{\sum\limits_{k = 1}^{N}\left( {{{Wd}(k)}^{H}{{Vd}\left( {m,k} \right)}{{Vd}\left( {m,k} \right)}^{H}{{Wd}(k)}} \right)} + {{\sigma (m)}}^{2}}} & (26)\end{matrix}$

where

-   -   σ (m): noise power of mth terminal station    -   Re: real number portion    -   suffix H: complex conjugate transposition

${{Wd}(n)} = \begin{pmatrix}{{wd}\left( {n,1} \right)} \\{{wd}\left( {n,2} \right)} \\\vdots \\{{wd}\left( {n,P} \right)}\end{pmatrix}$

-   -   wd(n,1) to wd(n,P): weights for antenna elements    -   P: number of antenna elements of nth base station    -   Vd(m,n): transfer function vector of downlink communication        between mth terminal station and nth base station

${{Vd}\left( {m,n} \right)} = \begin{pmatrix}{{vd}\left( {m,n,1} \right)} \\{{vd}\left( {m,n,2} \right)} \\\vdots \\{{vd}\left( {m,n,P} \right)}\end{pmatrix}$

-   -   vd(m,n,1) to vd(m,n,P): transfer functions of antenna elements    -   N: number of base stations    -   K: number of terminal stations    -   Assume communication between nth base station and mth terminal        station

In step S23, the weight vector obtained in step S22 is substituted as aninitial value into a weight vector Wd(n) of equation (25). In step S24,a gain G(m) of equation (26) is calculated. In step S25, the weightvector Wd(n) of equation (25) is re-calculated using the gain G(m).

Until the arithmetic result converges, calculations in steps S24 and S25are alternately repeated. In step S26, it is identified whether thearithmetic result has converged. For this determination, for example, asignal-to-interference-power ratio in a communication channel with alowest transmission quality is compared with a predetermined thresholdvalue. That is, it can be regarded that the arithmetic result hasconverged when the transmission quality of a most degraded communicationchannel exceeds the lower limit value.

When the arithmetic result has converged, the flow advances from stepS26 to S27 to transmit the weight vector Wd(n) as the final arithmeticresult to each base station 102.

In the second embodiment as well, the directional patterns of theantennas of the plurality of base stations 102 can be controlledaltogether.

An arithmetic result convergence characteristic in executing the controlshown in FIG. 4 was simulated using a computer. FIG. 8 shows the result.This simulation was done assuming the following conditions.

-   -   Number of base stations: 2    -   Number of terminal stations: 2    -   Distance between base stations: 500 m

Also assume that the transfer functions could be estimated without anyerror. Referring to FIG. 8, the control shown in FIG. 4 does not divergebut converge with update about 100 times. An interference characteristicin employing the control shown in FIG. 4 was simulated, andconsequently, a result that completely matched FIG. 6 was obtained.

That is, even in executing the control shown in FIG. 4, the downlinkdirectional patterns of the base stations can be determined altogethersuch that the total interference power in the plurality of communicationchannels is minimized, as in the first embodiment.

Control of the uplink will be described first with reference to FIG. 5.As in FIG. 2, transfer functions estimated by each base station 102 areinput to the intensive control station 103. On the basis of the transferfunctions, the intensive control station 103 determines the uplinkdirectional pattern of the antenna of each base station 102 and thetransmission power of each terminal station 101.

When transfer functions necessary for control are input, processing bythe intensive control station 103 advances from step S41 to S42. In stepS42, a conventional adaptive antenna control algorithm (e.g., R. A.Monzingo and T. W. Miller, “Introduction to Adaptive Arrays”, John Wiley& Sons, Inc. 1980) is applied to each base station 102, therebyobtaining the uplink weight vector of the adaptive antenna of each basestation 102 for autonomous distributed control

$\begin{matrix}{{{Wu}(n)} = {{{Gt}(m)}\left( {\sum\limits_{k = 1}^{K}{{{Gt}(k)}^{2}{{Vu}\left( {k,n} \right)}{{Vu}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vu}\left( {m,n} \right)}}} & (3) \\{{{Gt}(m)} = \frac{{Re}\left( {{{Wu}(n)}^{H}{{Vu}\left( {m,n} \right)}} \right)}{\begin{matrix}{{\sum\limits_{k = 1}^{N}\left( {{{Wu}(k)}^{H}{{Vu}\left( {m,k} \right)}{{Vu}\left( {m,n} \right)}^{H}{{Wu}(k)}} \right)} +} \\\left( {{{Wu}(n)}^{H}{{Wu}(n)}{{\sigma (m)}}^{2}} \right)\end{matrix}}} & (4)\end{matrix}$

-   -   where    -   σ (n): input noise power of nth base station    -   Wu(n): weight vector of nth adaptive antenna system    -   Re: real number portion    -   suffix H: complex conjugate transposition

${{Wu}(n)} = \begin{pmatrix}{{wu}\left( {n,1} \right)} \\{{wu}\left( {n,2} \right)} \\\vdots \\{{wu}\left( {n,P} \right)}\end{pmatrix}$

-   -   wu(n,1) to wu(n,P): weights for antenna elements    -   P: number of antenna elements of nth base station    -   Vu(m,n): transfer function vector of uplink communication        between mth terminal station and nth base station

${{Vu}\left( {m,n} \right)} = \begin{pmatrix}{{vu}\left( {m,n,1} \right)} \\{{vu}\left( {m,n,2} \right)} \\\vdots \\{{vu}\left( {m,n,P} \right)}\end{pmatrix}$

-   -   vu(m,n,1) to vu(m,n,P): transfer functions of antenna elements    -   N: number of base stations    -   K: number of terminal stations    -   Assume communication between nth base station and mth terminal        station

In step S43, the weight vector obtained in step S42 is substituted as aninitial value into a weight vector Wu(n) of equation (27). In step S44,a transmission power Gt(m) of equation (28) is calculated. In step S45,the weight vector Wu(n) of equation (27) is re-calculated using thetransmission power Gt(m).

Until the arithmetic result converges, calculations in steps S44 and S45are alternately repeated. In step S46, it is identified whether thearithmetic result has converged. For this determination, for example, asignal-to-interference-power ratio in a communication channel with alowest transmission quality is compared with a predetermined thresholdvalue. That is, it can be regarded that the arithmetic result hasconverged when the transmission quality of a most degraded communicationchannel exceeds the lower limit value.

When the arithmetic result has converged, the flow advances from stepS46 to S47 to transmit the weight vector Wu(n) as the final arithmeticresult to each base station 102. In addition, the transmission powerGt(m) as the final arithmetic result is transmitted to each terminalstation 101. In the second embodiment as well, the uplink directionalpatterns of the antennas of the plurality of base stations 102 and thetransmission powers of the plurality of terminal stations 101 can becontrolled altogether.

An arithmetic result convergence characteristic in executing the controlshown in FIG. 5 was simulated using a computer. The same result as inFIG. 8 was obtained. That is, even in executing the control shown inFIG. 5, the uplink directional patterns of the base stations and thetransmission powers of the terminal stations can be determinedaltogether such that the total interference power in the plurality ofcommunication channels is minimized, as in the first embodiment.

Third Embodiment

FIG. 10 shows the third embodiment. This third embodiment corresponds toclaims 11 to 24.

Claims 11 and 12 are to control the directivity of the antenna of eachbase station on the basis of transmission/reception signals exchangedbetween two or more base stations and two or more terminal stations.

That is, as shown in FIG. 10, at least two terminal stations 101A and101B are present in radio zones A and B of a plurality of base stations102A and 102B. When the terminal stations 101A and 101B aretransmitting/receiving radio wave signals to/from the base stations 102Aand 102B, respectively, using the same communication channel with thesame frequency and same timing, an intensive control station 103receives through the terminal stations 101A and 101B at least one of thetransmission signal from each of the terminal stations 101A and 101B andthe reception signal at each of the terminal stations 101A and 101B,which is received and transmitted by each of the terminal stations 101Aand 101B, generates weight vectors for minimizing the interference poweron the basis of the received signals, and transmits the weight vectorsto the base stations 102A and 102B as control signals to change thedirectivity characteristics of the antennas of the base stations 102Aand 102B such that the interference power between the terminal stations101A and 101B is reduced.

In this case, the base stations 102A and 102B are connected, and theabove-described function of the intensive control station 103 isimparted to one of the base stations 102A and 102B, e.g., the basestation 102A to cause the base station 102A to receive through the basestation 102B a signal from the terminal station 101B that iscommunicating with the base station 102B and also receive a signal fromthe terminal station 101A connected to itself. On the basis of thereceived signals, the base station 102A generates control signals forreducing the interference power between the terminal stations 101A and101B to change the directivity of antenna of itself and also to changethe directivity characteristic of the antenna of the base station 102Bby transmitting the generated control signal to the base station 102B.With this arrangement, the intensive control station 103 can be omitted.

As described in claim 13, the intensive control station 103 obtains thefield strength and spatial correlation characteristic of each basestation on the basis of a signal transferred from each base station anddetermines, on the basis of the obtained field strength and spatialcorrelation characteristic, a base station whose directivitycharacteristic of the antenna is to be changed.

Generally, when the terminal stations 101A and 101B which execute radiocommunication with the base stations 102A and 102B, respectively, arepresent on lines that connect the base stations 102A and 102B, as shownin FIG. 10, the spatial correlation characteristic of each of the basestations 102A and 102B is supposed to be high. In claim 13, when aplurality of base stations are present, the intensive control station103 receives a signal transferred from each base station and obtains thefield strength and spatial correlation characteristic of each basestation on the basis of the received signal. When at least one of thebase stations has a high spatial correlation characteristic, the basestations 102A and 102B which have high reception field levels and thepositional relationship as shown in FIG. 10 are selected and determinedas base stations whose directivity characteristics of the antennas areto be changed.

In each of the base stations 102A and 102B, an antenna comprises aplurality of antenna elements 901, and weighting circuits 902 and 912for respectively weighting the transmission/reception signals to/fromthe plurality of antenna elements, as shown in FIG. 9 described above.The directivity characteristic of the antenna is changed by causing theweighting circuits to weight the transmission/reception signalstransmitted/received to/from the plurality of antenna elements. That is,as in claim 14, a base station has an adaptive antenna comprising anantenna formed from a plurality of antenna elements, and weightingcircuits for respectively weighting the transmission/reception signalsto/from the plurality of antenna elements, and the directivitycharacteristic of the antenna is changed by causing the weightingcircuits to weight the transmission/reception signalstransmitted/received to/from the plurality of antenna elements.

In the terminal stations 101A and 101B, upon receiving signalstransmitted from the plurality of neighboring base stations 102A and102B, transfer functions are estimated as described above by checkingthe correlation between the reception signals and known signals held bythemselves in advance. The estimated transfer functions are transmittedto the base stations 102A and 102B. Upon receiving the transferfunctions, the base stations 102A and 102B transmit the transferfunctions to the intensive control station 103. As in claim 16, theintensive control station 103 calculates weight vectors using, asparameters, the transfer functions and the predicted values of thereception levels of the terminal stations. On the basis of thecalculated weight vectors, the intensive control station 103 calculatesthe sum of square errors between the reception signals (i.e.,transmission signals of the base stations 102A and 102B) at the terminalstations 101A and 101B using the same communication channel and desiredsignals d corresponding to the reception signals and repeatedlycalculates the weight vectors by repeatedly changing the parametersuntil the sum of square errors becomes smaller than a predeterminedthreshold value. On the basis of weight vectors obtained when the sum ofsquare errors becomes smaller than the threshold value, the weights ofthe antennas of the base stations 102A and 102B are determined. In thiscase, as in claim 15, the above-described function of the intensivecontrol station 103 may be imparted to the base stations 102A and 102Bsuch that the base stations 102A and 102B change the directivitycharacteristics of their antennas on the basis of the transfer functionsreceived from the terminal stations 101A and 101B.

In this case, as in claim 17, on the basis of the calculated weightvectors, the sum of square errors between the reception signals at theterminal stations 101A and 101B using the same communication channel andthe desired signals d corresponding to the reception signals may becalculated, and the weight vectors may be repeatedly calculated byrepeatedly changing the parameters until the maximum value of squareerrors at the terminal stations 101A and 101B becomes smaller than. apredetermined threshold value. On the basis of weight vectors obtainedwhen the maximum of square errors becomes smaller than the thresholdvalue, the weights of the antennas of the base stations 102A and 102Bmay be determined.

The above method can be actually realized by executing the processing insteps S23 to S26 shown in the flow chart of FIG. 4. That is, as in claim18, a weight vector obtained in step S22 of FIG. 4 is substituted as aninitial value into a weight vector Wd(n) of equation (25). In step S24,a gain (the reciprocal of the predicted value of the reception level)G(m) of equation (26) is calculated. In step S25, the weight vectorWd(n) of equation (25) is re-calculated using the gain G(m). Until thearithmetic result converges, calculations in steps S24 and S25 arealternately repeated. In this case, as in claim 19, asignal-to-interference-power ratio in a communication channel with alowest transmission quality may be defined as the threshold value, andthe weights of the antennas of the base stations 102A and 102B may bedetermined on the basis of the weight vectors obtained when the maximumvalue of the square errors becomes smaller than the threshold value.

In the base stations 102A and 102B, upon receiving signals transmittedfrom the terminal stations 101A and 101B, transfer functions areestimated as described above by checking the correlation between thereception signals and known signals held by themselves in advance. Theestimated transfer functions are transmitted to the intensive controlstation 103. As in claim 21, the intensive control station 103calculates weight vectors using, as parameters, the transfer functionsand transmission power values to be set for the terminal stations 101Aand 101B. On the basis of the calculated weight vectors, the intensivecontrol station 103 calculates the sum of square errors between thetransmission signals (i.e., the reception signals of the base stations102A and 102B) at the terminal stations 101A and 101B using the samecommunication channel and the desired signals d corresponding to thetransmission signals and repeatedly calculates the weight vectors byrepeatedly changing the parameters until the sum of square errorsbecomes smaller than a predetermined threshold value. On the basis ofweight vectors obtained when the sum of square errors becomes smallerthan the threshold value, the weights of the antennas of the basestations 102A and 102B are determined. In this case, as in claim 20, theabove-described function of the intensive control station 103 may beimparted to the base stations 102A and 102B such that the base stations102A and 102B change the directivity characteristics of their antennason the basis of the transfer functions estimated by themselves.

In this case, as in claim 22, on the basis of the calculated weightvectors, the sum of square errors between the transmission signals atthe terminal stations 101A and 101B using the same communication channeland the desired signals d corresponding to the transmission signals maybe calculated, and the weight vectors may be repeatedly calculated byrepeatedly changing the parameters until the maximum value of squareerrors at the terminal stations 101A and 101B becomes smaller than apredetermined threshold value. On the basis of weight vectors obtainedwhen the maximum of square errors becomes smaller than the thresholdvalue, the weights of the antennas of the base stations 102A and 102Bmay be determined.

The above method can be actually realized by executing the processing insteps S43 to S46 shown in the flow chart of FIG. 5. That is, as in claim23, a weight vector obtained in step S43 of FIG. 5 is substituted as aninitial value into a weight vector Wu(n) of equation (27). In step S44,a transmission power Gt(m) of equation (28) is calculated. In step S45,the weight vector Wu(n) of equation (27) is re-calculated using thetransmission power Gt(m).

Until the arithmetic result converges, calculations in steps S44 and S45are alternately repeated. In this case, as in claim 24, asignal-to-interference-power ratio in a communication channel with alowest transmission quality may be defined as the threshold value, andthe weights of the antennas of the base stations 102A and 102B may bedetermined on the basis of the weight vectors obtained when the maximumvalue of the square errors becomes smaller than the threshold value.

As has been described above, according to the present invention, since aplurality of adaptive antennaes each having an interference reductioncapability are controlled altogether such that the total interferencepower at the terminal stations is minimized in the downlink and thetotal interference power at the base stations is minimized in the uplinkcommunication, the interference can be reduced in the entire system bothfor the uplink and downlink communications.

Hence, the distance between base stations which use the same frequencycan be made shorter than in a conventional adaptive antenna. That is,the frequency use efficiency can be improved, and a high-speed radiocommunication system that requires a wide frequency band can beimplemented within a limited band.

1. An adaptive antenna transmission/reception characteristic controlmethod characterized in that when a plurality of terminal stations(101A, 101B) are present in a radio zone where a plurality of radio basestations (102A, 102B) each having an antenna are present, and at leasttwo of the plurality of terminal stations are transmitting/receivingradio wave signals to/from different radio base stations using the samecommunication channel with the same signal transmission/receptionfrequency and same signal transmission/reception timing, at least one ofa transmission signal from each of the terminal stations and a receptionsignal at each of the terminal stations, which is received by andtransmitted from each of the terminal stations, is received through theplurality of radio base stations, and a directivity characteristic ofthe antenna of each base station is changed on the basis of the receivedsignals to reduce an interference power between the terminal stations.2. A method according to claim 1, wherein the transmission/receptionsignals of the terminal stations using the same communication channel,which are received through the radio base station, are transferred to anintensive control station (103), and the intensive control stationgenerates, on the basis of the transferred signals, a control signal forreducing the interference power between the terminal stations andtransmits the control signal to each radio base station, therebychanging the directivity characteristic of the antenna of each radiobase station.
 3. A method according to claim 2, wherein the intensivecontrol station obtains a field strength and spatial correlationcharacteristic of each radio base station on the basis of thetransferred signals and, on the basis of the obtained field strength andspatial correlation characteristic, determines a base station whosedirectivity characteristic of the antenna is to be changed.
 4. A methodaccording to claim 1, wherein each radio base station having an adaptiveantenna comprising the antenna formed from a plurality of antennaelements (901) and weighting circuits (912,902) for respectivelyweighting transmission/reception signals of the plurality of antennaelements, and the weighting circuits weight the transmission/receptionsignals transmitted/received from/by the plurality of antenna elements,thereby changing the directivity characteristic of the antenna.
 5. Amethod according to claim 4, wherein upon receiving signals transmittedfrom the plurality of neighboring radio base stations, each terminalstation estimates a transfer function by checking a correlation betweeneach of the reception signals and a known signal which is held by theterminal station in advance and transmits the transfer function to theradio base station, and each radio base station changes the directivitycharacteristic of the antenna on the basis of the received transferfunction.
 6. A method according to claim 5, wherein each radio basestation transmits to the intensive control station the transfer functiontransmitted from each terminal station, and the intensive controlstation calculates a weight vector Wd(i) (i=1 to n: n is the totalnumber of terminal stations), using as parameters, the transfer functionand a predicted value 1/G(i) (i=1 to n: n is the total number ofterminal stations) of a reception level of each terminal station, on thebasis of the calculated weight vector Wd(i), calculates a sum of squareerrors between the reception signals at the terminal stations whichsimultaneously use the same communication channel with the samefrequency and same timing and desired signals corresponding to thereception signals and repeatedly calculates the weight vector Wd(i)while repeatedly changing the parameters until the sum of the squareerrors becomes smaller than a predetermined threshold value, anddetermines the weight of the antenna of each radio base station on thebasis of the weight vector Wd(i) obtained when the sum of the squareerrors becomes smaller than the threshold value.
 7. A method accordingto claim 5, wherein each radio base station transmits to the intensivecontrol station the transfer function transmitted from each terminalstation, and the intensive control station calculates a weight vectorWd(i) (i=1 to n: n is the total number of terminal stations), using asparameters, the transfer function and a predicted value 1/G(i) (i=1 ton: n is the total number of terminal stations) of a reception level ofeach terminal station, on the basis of the calculated weight vectorWd(i), calculates a sum of square errors between the reception signalsat the terminal stations which simultaneously use the same communicationchannel with the same frequency and same timing and desired signalscorresponding to the reception signals and repeatedly calculates theweight vector Wd(i) while repeatedly changing the parameters until amaximum value of the square errors at each terminal station becomessmaller than a predetermined threshold value, and determines the weightof the antenna of each radio base station on the basis of the weightvector Wd(i) obtained when the maximum value of the square errorsbecomes smaller than the threshold value.
 8. A method according to claim6, wherein equation (5) representing a weight vector Wd(n) of atransmission system, which is to be given to the weighting circuit ofthe adaptive antenna of an nth radio base station, and equation (6)representing a predicted value 1/G(m) of the reception level of an mthterminal station, which is obtained by a directional pattern generatedby the adaptive antenna, are alternately repeatedly calculated, and theweight vector Wd(n) of a calculation result which has converged is usedas a value of the weight to be given to each weighting circuit:$\begin{matrix}{{{Wd}(n)} = {{G(m)}\left( {\sum\limits_{k = 1}^{K}{{G(k)}^{2}{{Vd}\left( {k,n} \right)}{{Vd}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vd}\left( {m,n} \right)}}} & (5) \\{{G(m)} = \frac{{Re}\left( {{{Wd}(n)}^{H}{{Vd}\left( {m,n} \right)}} \right)}{{\sum\limits_{k = 1}^{N}\left( {{{Wd}(k)}^{H}{{Vd}\left( {m,k} \right)}{{Vd}\left( {m,k} \right)}^{H}{{Wd}(k)}} \right)} + {{\sigma (m)}}^{2}}} & (6)\end{matrix}$ where σ (m): noise power of mth terminal station Re: realnumber portion suffix H: complex conjugate transposition${Wd} = \begin{pmatrix}{{wd}\left( {n,} \right)} \\{{wd}\left( {n,2} \right)} \\\vdots \\{{wd}\left( {n,P} \right)}\end{pmatrix}$ wd(n,1) to wd(n,P): weights for antenna elements P:number of antenna elements of nth base station Vd(m,n): transferfunction vector of downlink communication between mth terminal stationand nth base station ${{Vd}\left( {m,n} \right)} = \begin{pmatrix}{{vd}\left( {m,n,1} \right)} \\{{vd}\left( {m,n,2} \right)} \\\vdots \\{{vd}\left( {m,n,P} \right)}\end{pmatrix}$ vd(m,n,1) to vd(m,n,P): transfer functions of antennaelements N: number of base stations K: number of terminal stationsAssume communication between nth base station and mth terminal station9. A method according to claim 7, wherein equation (7) representing aweight vector Wd(n) of a transmission system, which is to be given tothe weighting circuit of the adaptive antenna of an nth radio basestation, and equation (8) representing a predicted value 1/G(m) of thereception level of an mth terminal station, which is obtained by adirectional pattern generated by the adaptive antenna, are alternatelyrepeatedly calculated, and the weight vector Wd(n) of a calculationresult which has converged is used as a value of the weight to be givento each weighting circuit: $\begin{matrix}{{{Wd}(n)} = {{G(m)}\left( {\sum\limits_{k = 1}^{K}{{G(k)}^{2}{{Vd}\left( {k,n} \right)}{{Vd}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vd}\left( {m,n} \right)}}} & (7) \\{{G(m)} = \frac{{Re}\left( {{{Wd}(n)}^{H}{{Vd}\left( {m,n} \right)}} \right)}{{\sum\limits_{k = 1}^{N}\left( {{{Wd}(k)}^{H}{{Vd}\left( {m,k} \right)}{{Vd}\left( {m,k} \right)}^{H}{{Wd}(k)}} \right)} + {{\sigma (m)}}^{2}}} & (8)\end{matrix}$ σ (m): noise power of mth terminal station Re: real numberportion suffix H: complex conjugate transposition${{Wd}(n)} = \begin{pmatrix}{{wd}\left( {n,} \right)} \\{{wd}\left( {n,2} \right)} \\\vdots \\{{wd}\left( {n,P} \right)}\end{pmatrix}$ wd(n,1) to wd(n,P): weights for antenna elements P:number of antenna elements of nth base station Vd(m,n): transferfunction vector of downlink communication between mth terminal stationand nth base station ${{Vd}\left( {m,n} \right)} = \begin{pmatrix}{{vd}\left( {m,n,1} \right)} \\{{vd}\left( {m,n,2} \right)} \\\vdots \\{{vd}\left( {m,n,P} \right)}\end{pmatrix}$ vd(m,n,1) to vd(m,n,P): transfer functions of antennaelements N: number of base stations K: number of terminal stationsAssume communication between nth base station and mth terminal station10. A method according to claim 4, wherein upon receiving signalstransmitted from the plurality of neighboring terminal stations, eachradio base station estimates a transfer function by checking acorrelation between each of the reception signals and a known signalwhich is held by the radio base station in advance and changes thedirectivity characteristic of the antenna of the radio base station onthe basis of the transfer function.
 11. A method according to claim 10,wherein each radio base station transmits the transfer function to theintensive control station, and the intensive control station calculatesa weight vector Wu(i) (i=1 to n: n is the total number of terminalstations), using as parameters, the transfer function and a transmissionpower value G(i) (i 1 to n: n is the total number of terminal stations)set for each terminal station, on the basis of the calculated weightvector Wu(i), calculates a sum of square errors between the transmissionsignals at the terminal stations which simultaneously use the samecommunication channel with the same frequency and same timing anddesired signals corresponding to the transmission signals and repeatedlycalculates the weight vector Wu(i) while repeatedly changing theparameters until the sum of the square errors becomes smaller than apredetermined threshold value, and determines the weight of the antennaof each radio base station on the basis of the weight vector Wu(i)obtained when the sum of the square errors becomes smaller than thethreshold value.
 12. A method according to claim 10, wherein each radiobase station transmits the transfer function to the intensive controlstation, and the intensive control station calculates a weight vectorWu(i) (i=1 to n: n is the total number of terminal stations), using asparameters, the transfer function and a transmission power value G(i)(i=1 to n: n is the total number of terminal stations) set for eachterminal station, on the basis of the calculated weight vector Wu(i),calculates a sum of square errors between the transmission signals atthe terminal stations which simultaneously use the same communicationchannel with the same frequency and same timing and desired signalscorresponding to the transmission signals and repeatedly calculates theweight vector Wu(i) while repeatedly changing the parameters until amaximum value of the square errors at each terminal station becomessmaller than a predetermined threshold value, and determines the weightof the antenna of each radio base station on the basis of the weightvector Wu(i) obtained when the maximum value of the square errorsbecomes smaller than the threshold value.
 13. A method according toclaim 11, wherein equation (9) representing a weight vector Wu(n) of areception system, which is to be given to the weighting circuit of theadaptive antenna of an nth radio base station, and equation (10)representing a transmission power Gt(m) of an mth terminal station arealternately repeatedly calculated, and the weight vector Wu(n) of acalculation result which has converged is used as a weight to be givento each weighting circuit: $\begin{matrix}{{{Wu}(n)} = {{G(m)}\left( {\sum\limits_{k = 1}^{K}{{G(k)}^{2}{{Vu}\left( {k,n} \right)}{{Vu}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vu}\left( {m,n} \right)}}} & (3) \\{{{Gt}(m)} = \frac{{Re}\left( {{{Wu}(n)}^{H}{{Vu}\left( {m,n} \right)}} \right)}{\begin{matrix}{{\sum\limits_{k = 1}^{N}\left( {{{Wu}(k)}^{H}{{Vu}\left( {m,k} \right)}{{Vu}\left( {m,k} \right)}^{H}{{Wu}(k)}} \right)} +} \\\left( {{{Wu}(n)}^{H}{{Wu}(n)}{{\sigma (m)}}^{2}} \right)\end{matrix}}} & (4)\end{matrix}$ where σ (n): input noise power of nth base station Wu(n):weight vector of nth adaptive antenna system Re: real number portionsuffix H: complex conjugate transposition ${{Wu}(n)} = \begin{pmatrix}{{wu}\left( {n,1} \right)} \\{{wu}\left( {n,2} \right)} \\\vdots \\{{wu}\left( {n,P} \right)}\end{pmatrix}$ wu(n,1) to wu(n,P): weights for antenna elements P:number of antenna elements of nth base station Vu(m,n): transferfunction vector of uplink communication between mth terminal station andnth base station ${{Vu}\left( {m,n} \right)} = \begin{pmatrix}{{vu}\left( {m,n,1} \right)} \\{{vu}\left( {m,n,2} \right)} \\\vdots \\{{vu}\left( {m,n,P} \right)}\end{pmatrix}$ vu(m,n,1) to vu(m,n,P): transfer functions of antennaelements N: number of base stations K: number of terminal stationsAssume communication between nth base station and mth terminal station.14. A method according to claim 12, wherein equation (11) representing aweight vector Wu(n) of a reception system, which is to be given to theweighting circuit of the adaptive antenna of an nth radio base station,and equation (12) representing a transmission power Gt(m) of an mthterminal station are alternately repeatedly calculated, and the weightvector Wu(n) of a calculation result which has converged is used as aweight to be given to each weighting circuit: $\begin{matrix}{{{Wu}(n)} = {{G(m)}\left( {\sum\limits_{k = 1}^{K}{{G(k)}^{2}{V\left( {k,n} \right)}{{Vd}\left( {k,n} \right)}^{H}}} \right)^{- 1}{{Vd}\left( {m,n} \right)}}} & (3) \\{{{Gt}(m)} = \frac{{Re}\left( {{{Wu}(n)}^{H}{{Vu}\left( {m,n} \right)}} \right)}{\begin{matrix}{{\sum\limits_{k = 1}^{N}\left( {{{Wu}(k)}^{H}{{Vu}\left( {m,k} \right)}{{Vu}\left( {m,k} \right)}^{H}{{Wu}(k)}} \right)} +} \\\left( {{{Wu}(n)}^{H}{{Wu}(n)}{{\sigma (m)}}^{2}} \right)\end{matrix}}} & (4)\end{matrix}$ where a(n): input noise power of nth base station Wu(n):weight vector of nth adaptive antenna system Re: real number portionsuffix H: complex conjugate transposition ${{Wu}(n)} = \begin{pmatrix}{{wu}\left( {n,1} \right)} \\{{wu}\left( {n,2} \right)} \\\vdots \\{{wu}\left( {n,P} \right)}\end{pmatrix}$ wu(n,1) to wu(n,P): weights for antenna elements P:number of antenna elements of nth base station Vu(m,n): transferfunction vector of uplink communication between mth terminal station andnth base station. ${{Vu}\left( {m,n} \right)} = \begin{pmatrix}{{vu}\left( {m,n,1} \right)} \\{{vu}\left( {m,n,2} \right)} \\\vdots \\{{vu}\left( {m,n,P} \right)}\end{pmatrix}$ vu(m,n,1) to vu(m,n,P): transfer functions of antennaelements N: number of base stations K: number of terminal stationsAssume communication between nth base station and mth terminal station